In recent years, in order to achieve high breakdown voltage, low loss, and utilization of semiconductor devices under a high temperature environment, silicon carbide has begun to be adopted as a material for a semiconductor device. Silicon carbide is a wide band gap semiconductor having a band gap larger than that of silicon, which has been conventionally widely used as a material for semiconductor devices.
Hence, by adopting silicon carbide as a material for a semiconductor device, the semiconductor device can have a high breakdown voltage, reduced on resistance, and the like. Further, the semiconductor device thus adopting silicon carbide as its material has characteristics less deteriorated even under a high temperature environment than those of a semiconductor device adopting silicon as its material, advantageously.
Japanese Patent Laying-Open No. 2010-258294 discloses a method for manufacturing a MOSFET (Metal Oxide Semiconductor Field Effect Transistor) having a trench structure. According to the method for manufacturing the MOSFET, a corner portion constituting an opening of the trench is rounded by performing heat treatment after forming the trench. Accordingly, occurrence of gate leakage is suppressed in a gate insulating film formed on the rounded corner portion.